Clutch slipping when it get hot

The clutch is new and the pressure plate is also new. I've having this problem since the vehicle have 40,000 miles(new). The vehicle is a 1989 Isuzu Amigo 2.6L(4X4) . There is no oil on the clutch or pressure plate. I have this car since 1992. The problem is, this is the fourth time the vehicle have this problem. The vehicle have been properly maintained and is in perfect conditions.What I am thinking is that the flywheel is the problem even though it have been set for correction to a machine shop. Also the hydraulic cylinders of the clutch have been replaced. Also there is no air on the hydraulic system it have been properly bleed ed. The problem occurs when the car is in a traffic jam after a while the clutch start slipping when shifting gears.

2 Answers

My cousin has a 93 2.6L 2 wheel drive Amigo. She was driving u a hill when the clutch started slipping, she had only purchased/started driving the vehicle 6 months before the clutch Slipping occured. I took the Trans out, resurfaced the flywheel, installed a new pilot bearing in the crankshaft, installed a new non factory pressure plate, clutch disc and throw out bearing. I put the trans back in aaand it continued to slip in the exact same way : / . Took trans out a second time, replaced resurfaced flywheel with brand new flywheel, adjusted the clutch pedal to 6.71-7.13 inches from the floor to ensure that the return hole in the clutch master cylinder was not blocked by inner piston. Put everything back together and it STILL! friken slipped like crazy, vehicle wouldn't accelerate quickly and it could not travel faster then 50mph in any gear.

I've read all over the internet and I even talked to the Isuzu dealership shop foreman who said that once the clutch pedal is adjusted correctly the throwout bearing fork/clutch slave should be able to be pushed back/into itself with just a thumb or by hand, if you can't press it back with just a hand then the pedal is misadjusted. He also mentioned that many models have the throw out bearing constantly touching the clutch pressure plate, this is normal on the amigo if its a light ,only just making contact pressure. However if you have a mis-adjusted pedal possibly what could occur is that heat will expand the fluid in the line and will force the pressure into the clutch slave cylinder and press on the clutch as if you were slightly pressing on the pedal and the clutch would begin to slip.

it's my process of elimination hypothesis that . . . either the flywheel's outer diameter raised surface should be machined down some to cause the pressure plate to bolt down lower, causing the pressure plate , pressure surface to push farther up into itself when it makes contact with the clutch disc to give it more spring pressure. OR the clutch disc needs to be thicker causing the same thing oor the pressure plate is weak and needs to be replaced w a more performance brand higher pressure version of a stock pressure plate. Those are the last 3 possible causes of clutch grip failure aka clutch slip.

I found that the correct flywheel "step" spec (its actually called a "cup" spec to a machinist) is .157"-.159" (this is about 5/32 of an inch). If you have a machined flywheel and the shop cuts the center too deep it throws this measurement off, also if they cut the "step" down too far it throws this spec off. If you find that the flywheel has way more then .159" difference between the flat center and the stepped up circumference of the flywheel, that will cause slipping. (oppositely . . if your spec is less this will add a little more grip but if you travel too far off spec your clutch might not be able to release all the way).

I measured my cousins flywheel after I removed the flywheel a 3rd! time!!. and her new flywheel and resurfaced flywheel were up to spec as far as the step cut was concerned. I took both her used clutch and this "new" clutch to Kragen O'Reilly Auto parts and asked them to let me compare mine to the Sachs brand clutch kit they had . . Majjjooor difference. The cheap no name brand clutches my cousin had several obvious design corners cut.

Here are my observations :

1. the 3 springs on the cheap brand pressure plate had a slight S shape bend to them but they were almost totally straight bars of metal (and by springs i mean flat almost wide popsicle stick bars of metal not coil springs). The Sachs pressure plate springs were very much S shaped and had a much springier look to them.

2. The pressure plate springs on the no name brand pressure plate had the springs attaching to the circular pressure diaphram half way into the friction ring itself. WHile the Sachs brand had a full curcular disc of uninterrupted flat metal friction surface and the springs were attached on an outer chunk of metal.

3. The Sachs brand pressure plate had a guide pin next to ea spring an a chunk of metal molded into the pressure diaphram that rode along the pin. The cheap brand had no such thing.

4. The thickness of the Sachs pressure plate surface was thicker and had a ring texture molded into it (I hear most ppl rubb a little sand paper on this to break up the ring texture before installation to speed up clutch break in). The no name brand Pressure plate was flat and very thin.

5. The Sachs pressure plate "fingers" were almost totally flat before even installed on the flywheel. The no name brand pressure plate "fingers" were cone shaped before installation and after installation the "fingers" never became flat, they were still slightly aimed in a cone which to me was causing the throw out bearing to overly wear into the "fingers" on my cousins 1st dead clutch. The throw out bearing on the Isuzu Amigo, Rodeo, Maybe trooper and Honda Passport with a 2.3 or 2.6L engine is supposed to slightly always make contact with the pressure plate so this is normal no matter what clutch you use , I just noticed there was extra wear in the bearing because of the cheap brand pressure plate geometry.

6. The hinge mechanism in the no name pressure plate had pins holding it in that were not joined together, they dont need to be but the sachs brand pressure plate had a curcular ring holding the mechanism down .

7. The Sachs brand had way more rivets holding it together in general.

8. The Clutch discs themselves were similar however the Sachs brand springs were thicker and had more turns in them.

9. The Sachs clutch disc was slightly larger in diameter, I'm talking maybe 1/32 of an inch. And also about 2/32 of an inch (1/16th) thicker then the no name brand clutch disc.

10. The Sachs Clutch disc also ha more rivets holding it together and larger rivets that would fill up the rivet holes in the friction material completely on both sides of the disc.

So I suggested my cousin purchase this Sachs Clutch Kit. I installed it that day. And the Amigo ran without slipping :].

They recommend you break in a clutch easily for around 300 miles with simple shift driving before you can gun it and abuse your clutch however you abuse it.

Apparently if you put that new clutch in and gun it without breaking it in, you can ruin that brand new clutch that 1st test drive /day.

Hope this Helps anyone who is going nuts like i was with this issue.

p.s. If you install a new master or slave clutch cylinder, the high hard line that goes from the master up and over the brake booster and over to the passenger side of the vehicle , that whole section of tubing is a high spot where air will bubble up to and collect in. If you have trouble pedal bleeding you will need a brake line vacuum hand pump to power **** the air out and then the line will be bled.

The pedal itself must be adjusted to 6.73"-7.13" above the ground measured from the flat area behind the brake pedal to the top of the clutch pedal foot pad. There is a yellow/goldish rod connected to the top of the clutch pedal with a set nut. loosen the nut, twist the rod itself and that will bring the pedal higher or lower. set it to the correct height and set the nut. The front of the pedal may have a front stopper bolt. loosen the bolts set nut and unscrew the bolt back and away from the pedal before you adjust the pedal height so that once the pedal height is set you can set the front stopper bolt . Screw the stopper bolt in twords the pedal until it just touches the pedal and then turn it 1/2 a turn more and tighten the set nut.

Adjusting this correctly allows the piston in the clutch master cylinder to return all the way back to its resting position, when the piston is in its correct resting position it does not block a return hole build into the master cylinder to allow for fluid expansion in the line. If you have adjusted the pedal correctly and the return hole is not blocked you will be able to crawl under the vehicle and depress the clutch fork with a thumb and cause the slave cylinder rod to push into the slave cylinder . If you press on the clutch fork and it wont move, or requires allot of force to move, then you have not adjusted the pedal height correctly.Update:
IT WAS THE NEW CLUTCH!
I found that the correct flywheel "step" spec (its actually called a "cup" spec to a machinist) is .157"-.159" (this is about 5/32 of an inch). If you have a machined flywheel and the shop cuts the center too deep it throws this measurement off, also if they cut the "step" down too far it throws this spec off. If you find that the flywheel has way more then .159" difference between the flat center and the stepped up circumference of the flywheel, that will cause slipping. (oppositely . . if your spec is less this will add a little more grip but if you travel too far off spec your clutch might not be able to release all the way).
I measured my cousins flywheel after I removed the flywheel a 3rd! time!!. and her new flywheel and resurfaced flywheel were up to spec as far as the step cut was concerned. I took both her used clutch and this "new" clutch to Kragen O'Reilly Auto parts and asked them to let me compare mine to the Sachs brand clutch kit they had . . Majjjooor difference. The cheap no name brand clutches my cousin had several obvious design corners cut.
Here are my observations :
1. the 3 springs on the cheap brand pressure plate had a slight S shape bend to them but they were almost totally straight bars of metal (and by springs i mean flat almost wide popsicle stick bars of metal not coil springs). The Sachs pressure plate springs were very much S shaped and had a much springier look to them.
2. The pressure plate springs on the no name brand pressure plate had the springs attaching to the circular pressure diaphram half way into the friction ring itself. WHile the Sachs brand had a full curcular disc of uninterrupted flat metal friction surface and the springs were attached on an outer chunk of metal.
3. The Sachs brand pressure plate had a guide pin next to ea spring an a chunk of metal molded into the pressure diaphram that rode along the pin. The cheap brand had no such thing.
4. The thickness of the Sachs pressure plate surface was thicker and had a ring texture molded into it (I hear most ppl rubb a little sand paper on this to break up the ring texture before installation to speed up clutch break in). The no name brand Pressure plate was flat and very thin.
5. The Sachs pressure plate "fingers" were almost totally flat before even installed on the flywheel. The no name brand pressure plate "fingers" were cone shaped before installation and after installation the "fingers" never became flat, they were still slightly aimed in a cone which to me was causing the throw out bearing to overly wear into the "fingers" on my cousins 1st dead clutch. The throw out bearing on the Isuzu Amigo, Rodeo, Maybe trooper and Honda Passport with a 2.3 or 2.6L engine is supposed to slightly always make contact with the pressure plate so this is normal no matter what clutch you use , I just noticed there was extra wear in the bearing because of the cheap brand pressure plate geometry.
6. The hinge mechanism in the no name pressure plate had pins holding it in that were not joined together, they dont need to be but the sachs brand pressure plate had a curcular ring holding the mechanism down .
7. The Sachs brand had way more rivets holding it together in general.
8. The Clutch discs themselves were similar however the Sachs brand springs were thicker and had more turns in them.
9. The Sachs clutch disc was slightly larger in diameter, I'm talking maybe 1/32 of an inch. And also about 2/32 of an inch (1/16th) thicker then the no name brand clutch disc.
10. The Sachs Clutch disc also ha more rivets holding it together and larger rivets that would fill up the rivet holes in the friction material completely on both sides of the disc.
So I suggested my cousin purchase this Sachs Clutch Kit. I installed it that day. And the Amigo ran without slipping :].
They recommend you break in a clutch easily for around 300 miles with simple shift driving before you can gun it and abuse your clutch however you abuse it.
Apparently if you put that new clutch in and gun it without breaking it in, you can ruin that brand new clutch that 1st test drive /day.
Hope this Helps anyone who is going nuts like i was with this issue.
p.s. If you install a new master or slave clutch cylinder, the high hard line that goes from the master up and over the brake booster and over to the passenger side of the vehicle , that whole section of tubing is a high spot where air will bubble up to and collect in. If you have trouble pedal bleeding you will need a brake line vacuum hand pump to power **** the air out and then the line will be bled.
The pedal itself must be adjusted to 6.73"-7.13" above the ground measured from the flat area behind the brake pedal to the top of the clutch pedal foot pad. There is a yellow/goldish rod connected to the top of the clutch pedal with a set nut. loosen the nut, twist the rod itself and that will bring the pedal higher or lower. set it to the correct height and set the nut. The front of the pedal may have a front stopper bolt. loosen the bolts set nut and unscrew the bolt back and away from the pedal before you adjust the pedal height so that once the pedal height is set you can set the front stopper bolt . Screw the stopper bolt in twords the pedal until it just touches the pedal and then turn it 1/2 a turn more and tighten the set nut.
Adjusting this correctly allows the piston in the clutch master cylinder to return all the way back to its resting position, when the piston is in its correct resting position it does not block a return hole build into the master cylinder to allow for fluid expansion in the line. If you have adjusted the pedal correctly and the return hole is not blocked you will be able to crawl under the vehicle and depress the clutch fork with a thumb and cause the slave cylinder rod to push into the slave cylinder . If you press on the clutch fork and it wont move, or requires allot of force to move, then you have not adjusted the pedal height correctly.

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Related Questions:

I suspect that the full engagement of the clutch pressure plate is not being achieved
if a pressure plate is held at reduced application pressure , it will continuously slip marginally and this build up to a point where the clutch plate will not absorb any more heat and so it fades and slips completely ( same affect as brake fade from worn pads and too heavy brake application -like long down hill runs )
the area I would check is the clutch master cylinder as it appears that the compensating port is blocked , and holding pressure in the clutch line which with increasing heat from the clutch builds up more pressure and compounds the pressure plate problem
this is identical to a heavy truck clutch problem where full testing produced no problems , yet at 100 miles and on a range the clutch failed completely but when cooled down again tested as good
on replacing the clutch pressure plate and clutch plate it was revealed by a clutch specialist shop that the pressure springs were actually weaker that specifications and were in fact allowing the clutch top slip and so go into the fade situation

Hi Timothy, The clutch plate is fitted between the gearbox and the engine. Adjustment is carried out by lengthening or shortening the push rod. Some manufactures have adjustments between the slave cylinder and the clutch folk (underneath the vehicle) while others have adjustments between the top of the clutch pedal and the master cylinder, and others require replacement of the rod with shorter or longer, depending if the clutch is engaging to low or too high. If the clutch is slipping it will probably be too late for adjustment and require replacement of the clutch plate and possibly the clutch cover (pressure plate) and maybe the thrust bearing, Regards John

Does it grind the gears in the transmission. If yes, it could be the
clutch/pressure plate. It could be the clutch hydraulic slave cylinder not
working. Check all these thing out before purchasing a new clutch/pressure
plate. When VW is running does if like the vehicle has no get up an on like
maybe the clutch is slipping. GB...stewbison

Excessive wear on clutches is usually from alot of heavy hauling, pulling heavy trailers. 40,000 miles is real excessive. If you can, I would take the access cover off the bottom of the bell housing and check to see if the pressure plate bolts aren't backing out. When the clutch was replaced they should have (or I would have ) used a thread lock on these bolts. There is always a lot of vibration in this area, and I have seen these bolts back out, on manual and automatic transmissions.

Lets start with what was replaced : Clutch pressure plate, throwout bearing,pilot bearing,input shaft bearing, was flywheel cut or replaced,Clutch cable or slave cylinder (whatever is applicable,) Lets see what repair shop says. Depending on what they say they did or didn't do we will take it from there.
keep me posted

did you bleed the hydralic clutch system on this vehicle? = air in system or not bleed properly.
most of the flywheels for this model were not to be machined...... however it is ok to machine these only slightly but you must machine the surface the clutch plate contacts with the same amount as the outer raised section the pressure plate bolts to.
new flywheels have painted stamped writing saying do not machine...so if hydralic system is ok find out about flywheel.
also may pay to check clamping force of pressure plate most clutch places can do this or some workshops that is if fingers on pressure plate are all at the same height, not broken or cracked..

you have 20k miles after the clutch has been changed, now are you used to drving clutch, secondly is it hydraulic or cable controled clutc?

if you are used to drving clutch sys probable cause is defective pressure plate or the throwout bearing is not fully releasing in other words the clutch is partialy applied all the time because of the re;ease bearing not fully releasing!!